Warewasher with water energy recovery system

Abstract

A warewash machine sump collects hot cleaning water that is recirculated in the chamber during cleaning. A drain line is for draining cleaning water from the sump. A fresh water input system includes at least a hot water input and a cold water input. The fresh water input system has a common input line in communication with the hot water input and the cold water input. A cold water input valve and hot water input valve are provided. The drain line and the common input line are arranged in a heat exchange relationship. A temperature sensor arrangement is associated with the drain line for determining temperature of the cleaning water traveling through the drain line. A controller controls the hot water input valve and cold water input valve based upon the temperature sensor arrangement output.

What is claimed is: 
     
       1. A warewash machine, comprising:
 a housing at least in part defining a chamber for cleaning wares; 
 a sump for collecting hot cleaning water that is recirculated in the chamber during cleaning; 
 a drain line for draining cleaning water from the sump; 
 a fresh water input system including at least a hot water input that receives hot water from a hot water source and a cold water input that receives cold water from a cold water source, the fresh water input system having a common input line in communication with the hot water input and the cold water input; 
 a cold water input valve for controlling input of cold water into the common input line; 
 a hot water input valve for controlling input of hot water into the common input line; 
 the drain line and the common input line arranged in a heat exchange relationship to enable heat from cleaning water traveling through the drain line to transfer heat to water traveling through the common input line; 
 a temperature sensor arrangement associated with the drain line for determining temperature of the cleaning water traveling through the drain line; 
 a controller that receives input from the temperature sensor arrangement and is configured to control the cold water input valve and the hot water input valve such that, during a draining operation, (i) if cleaning water traveling through the drain line is above a preselected temperature, the controller opens the cold water input valve to allow water from the cold water source to enter the common input line and (ii) if cleaning water traveling through the drain line is below the preselected temperature, the controller closes the cold water input valve. 
 
     
     
       2. The warewash machine of  claim 1 , wherein water flowing through the common input line is heated by cleaning water traveling through the drain line, the warewash machine further comprising a storage tank that receives water from the common input line once heated by cleaning water traveling through the drain line. 
     
     
       3. The warewash machine of  claim 2  further comprising:
 a rinse system; and 
 a pump configured to pump water from the storage tank toward the rinse system. 
 
     
     
       4. The warewash machine of  claim 3  further comprising a booster heater downstream of the storage tank and that receives water from the storage tank and is configured to heat the water prior to delivering the water to the rinse system. 
     
     
       5. The warewash machine of  claim 1 , wherein, the controller is configured such that during an initial fill operation, if the temperature sensor indicates to the controller that no water above the preselected temperature is traveling through the drain line, the controller responsively opens the hot water input valve to allow hot water to enter the common input line. 
     
     
       6. The warewash machine of  claim 1 , wherein the common input line is in a counterflow heat exchange relationship with the drain line. 
     
     
       7. The warewash machine of  claim 1 , wherein water flowing through the common input line from the cold water source is heated by cleaning water traveling through the drain line to a temperature of at least about 110 degrees F. during the draining operation. 
     
     
       8. The warewash machine of  claim 7 , wherein cleaning water flowing through the drain line is cooled to a temperature of less than about 140 degrees F. by the water from the cold water source traveling through the common input line. 
     
     
       9. The warewash machine of  claim 7 , wherein cleaning water flowing through the drain line is cooled to a temperature of less than about 130 degrees F. by the water from the cold water source traveling through the common input line. 
     
     
       10. The warewash machine of  claim 1 , wherein the controller is configured to repeatedly open and close the cold water input valve to provide pulses of water from the cold water source to the common drain line during a sump dumping operation where the sump is at least substantially emptied of cleaning water through the drain line. 
     
     
       11. The warewash machine of  claim 1  further comprising:
 a heat exchanger comprising the common input line and the drain line that are in the heat exchange relationship; and 
 a filter system located between the sump and the heat exchanger, the filter system in communication with the drain line and configured to filter the cleaning water before the cleaning water enters the heat exchanger; 
 wherein the temperature sensor is located along the drain line between the sump and the heat exchanger. 
 
     
     
       12. The warewash machine of  claim 11 , wherein the filter system comprises a housing and a filter within the housing, at least part of the filter being visible from outside the housing. 
     
     
       13. A warewash machine, comprising:
 a housing at least in part defining a chamber for cleaning wares; 
 a sump for collecting hot cleaning water that is recirculated in the chamber during cleaning; 
 a drain line for draining cleaning water from the sump; 
 a fresh water input system including at least a hot water input for receiving hot water from a hot water source and a cold water input for receiving cold water from a cold water source; 
 a cold water input valve for controlling input of cold water; 
 a hot water input valve for controlling input of hot water; 
 a heat exchanger arrangement between the drain line and a portion of the fresh water input system to enable heat from cleaning water traveling through the drain line to transfer to water traveling through the portion of the freshwater input system; 
 a temperature sensor arranged to determine at least one of temperature of cleaning water traveling through the drain line or temperature of fresh water leaving the heat exchanger arrangement; 
 a controller that receives input from the temperature sensor arrangement and is configured to control opening and closing of both the cold water input valve and the hot water input valve based at least in part upon sensed temperature. 
 
     
     
       14. A warewash machine, comprising:
 a housing at least in part defining a chamber for cleaning wares; 
 a sump for collecting hot cleaning water that is recirculated in the chamber during cleaning; 
 a drain line for draining cleaning water from the sump; 
 a fresh water input system including at least a hot water input for receiving hot water from a hot water source and a cold water input for receiving cold water from a cold water source; 
 a cold water input valve for controlling input of cold water; 
 a hot water input valve for controlling input of hot water; 
 a heat exchanger arrangement between the drain line and a portion of the fresh water input system to enable heat from cleaning water traveling through the drain line to transfer to water traveling through the portion of the freshwater input system; 
 a temperature sensor arranged to determine temperature of cleaning water traveling through the drain line; 
 a controller that receives input from the temperature sensor arrangement and is configured to control the cold water input valve and the hot water input valve such that during a water input operation when the temperature sensor indicates a temperature above a preselected temperature the cold water valve is opened and the hot water valve is closed and when the temperature sensor indicates a temperature below the preselected temperature the cold water valve is closed and the hot water valve is opened.